Method for processing high-contrast photographic elements

ABSTRACT

Processing high-contrast photographic elements, said elements comprising a silver halide emulsion layer in which the halide comprises at least about 50 mole percent chloride, in a continuous transport processing machine wherein the developer solution contains a carbonyl bisulfite-amine condensation product and said element contains a cadmium salt such as cadmium chloride.

United States Patent Inventor Kirby M. Milton Rochester, N.Y.

App]. No. 661,533

Filed Aug. 18, 1967 Patented Oct. 26, 1971 Assignee Eastman Kodak Company Rochester, N.Y.

METHOD FOR PROCESSING HIGH-CONTRAST PHOTOGRAPHIC ELEMENTS 14 Claims, No Drawings U.S. Cl 96/66.3, 96/66, 96/50 Int. Cl G03c 5/30, G030 5/26 Field of Search 96/66, 63,

[56] References Cited UNITED STATES PATENTS 2,388,816 11/1945 Bean 95/88 2,839,405 6/1958 Jones 96/107 Primary Examiner-Norman G. Torchin Assistant ExaminerEdward C. Kimlin Attorneys-W. H. J. Kline, B. D. Wiese and Harold E. Cole METHOD FOR PROCESSING HIGH-CONTRAST PHOTOGRAPHIC ELEMENTS BACKGROUND OF THE INVENTION 1 Field of the Invention This invention relates to photographic materials, their preparation and use. One aspect of the invention relates to a continuous process for processing exposed high-contrast photographic elements in a continuous transport-processing machine wherein certain developers must be employed in combination with photographic elements containing a cadmium salt in order to increase speed and effective contrast, eliminate or reduce drag lines and improve the shape and spacing of its H and D curve.

2. Description of the Prior Art In the graphic arts field, where it is desired to make photographic line and halftone reproductions, it is customary to employ emulsions having extremely high contrast. In development, the developing areas grow autocatalytically at a very high developing rate to produce and extremely high contrast which is necessary for halftone patterns. Developers for use with extremely high-contrast photographic films are quite different in composition from typical black-and-white film developers. In order to obtain very high contrast and sharp halftone dots, it has been the practice to formulate developers for such films from essentially hydroquinone, an alkali, an alkali metal bromide and a low level of sulfite ion. The low level of sulfite ion partially stabilizes the developer solution for a short period of time and isachieved in all known commercial developers of this type by the use of sodium formaldehyde bisulfite, which acts as a sulfite ion buffer. These developer solutions must be stored in two parts, however, since the sodium formaldehyde bisulfite will dissociate at a high pH to give not only the desired sulfite ion but an equimolar amount of formaldehyde which will react with hydroquinone to destroy its developing power.

In reproducingcontinuous tone material, it is customary to make a halftone photographic intermediate, usually a film negative, in which the gradations in tone are represented by differing sizes of dots of uniform density. The shape, density and uniformity of the halftone dots are closely correlated to the quality of the resulting picture.

The developer solutions for high-contrast films presently used in continuous transport processing machines also have a number of disadvantages. The photographic quality obtained with a given film is usually inferior to that obtained in careful tray processing. The sensitivity of high-contrast films to developer exhaustion products and variations in local developing agent concentration makes these films vulnerable to directional drag streaks in film halftone areas under conditions of machine processing. These drag streaks occur in areas of high development (5090 percent dots) which are adjacent to areas of low 90 (dot area of 20 percent or less). The drag streaks are formed by more development occurring because the developer which is dragged in from the area of low development contains more developing agent and less exhaustion products (primarily bromide ion) than the developer that would normally be in that area. The dots in a high-contrast film are also distorted and exhibit size changes depending on the orientation and direction of travel through the machine processor. This dot distortion is manifested by discontinuities or plateaus in the H and D curve of high-contrast films which are processed in continuous transport processing machines. The elimination or reduction of drag streaks and dot distortions would be a considerable advance in the art.

U.S. Pat. No. 2,839,405 of Jones issued June 17, 1958, dis- Closes the use of cadmium salts as antifoggants for photographic emulsions. There is no' disclosure in this patent, however, of processing high-contrast elements containing a cadmium salt in a continuous transport processing machine employing only certain developers to provide the improvements taught by the instant invention.

SUMMARY OF THE INVENTION In my invention, a continuous process is provided for processing an exposed, high-contrast photographic element comprising a support coated with a silver halide emulsion wherein said element is processed in one continuous motion by transporting it into and out of at least one processing solution in the manner shown, for example, by U.S. Pat. Nos. 3,025,779 of Russell and Kunz issued Mar. 20, I962; 3,078,024 of Sardeson issued Feb. 19, I963; 3,122,086 of Fitch issued Feb. 25, 1964; 3,149,551 of Cramer issued Sept. 22, I964; 3,156,173 of Meyer issued Nov. I0, 1964; and 3,224,356 of Fleisher and Hixon issued Feb. 21, 1965; and wherein said element is developed in a liquid developer composition comprising a developing agent and a carbonyl bisulfite-amine condensation product, and wherein said photographic element contains at least about 10 grams of a cadmium salt per mole of silver in said silver halide emulsion.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The developing agents which can be employed in the instant invention can be any of those suitable for the intended purpose. Useful silver halide developers, for example, include the dihydroxybenzenes such as hydroquinone; chlorohydroquinone; bromohydroquinone; isopropylhydroquinone; toluhydroquinone; methylhydroquinone; 2,3-dichlorohydroquinone; 2,5-dimethylhydroquinone; 2,3-dibromohydroquinone; l,4-dihydroxy-2-acetophenone-2,S-dimethylhydroquinone; 2,5-diethylhydroquinone; 2,S-di-p-phenethylhydroquinone; 2,S-dibenzoylamineohydroquinone; 2,5- diacetaminohydroquinone; etc. Esters of such compounds, e.g., formates and acetates can also be employed. These developing agents can be used alone or in any combination and can be employed in any concentration which is effective for development. A suitable concentration for the developing agent is from about 0.05 to about 0.05 mole per liter of developer composition and is preferably from about 0.1 to about 0.30 mole per liter of developer composition.

The carbonyl bisulfite-amine condensation products which can be used in the developer composition employed in my invention are preferably formaldehyde bisulfite-amine condensation products such as sodium-2-hydroxyethylaminomethane sulfonate; sodium-2-hydroxypropylaminomethane sulfonate; sodium-l,1-dimethyl-2-hydroxyethylaminomethane sulfonate; sodium-l,l-bis(hydroxymethyl)ethylaminomethane sulfonate; sodium-tris-(hydroxymethyl)methylaminomethane sulfonate; sodium-3-hydroxypropylaminomethane sulfonate; sodium-bis(2-hydroxyethyl)aminomethane sulfonate; sodium- N,N-bis[ 2-( l-hydroxy)propyllaminomethane sulfonate; sodium-N-isopropyl-N-2-hydroxyethyl)-aminomethane sulfonate; sodium-N-ethyl-N-(2-hydroxyethyl)-aminomethane sulfonate; and sodium-N-methyl-N-(Z-hydroxyethyl)- aminomethane sulfonate. The carbonyl bisulfite-amine condensation products can be used alone or in any combination and can be employed in any concentration which is effective to provide a low level of sulfite ion for the developer composition. A suitable concentration for the carbonyl bisulfite-amine condensation product is from about 0.1 to about 1.0 mole per liter of liquid developer composition and is preferably from about 0.25 to about 0.50 mole per liter of liquid developer composition.

The carbonyl bisulfite-amine condensation product can be added to the developer composition as a separate compound or formed in situ. Methods for preparing these compounds are disclosed, for example, in U.S. Pat. No. 2,388,816 of Bean is sued Nov. '13, 1945. In this specification and claims, it is meant to include within the definition of carbonyl bisulfiteamine condensation product either the compound itself or the individual components which form the compound in situ.

The high-contrast photographic elements which can be processed according to the instant invention comprise a silver halide emulsion layer in which the halide comprises at least about 50 mole percent chloride. Preferably the silver halide emulsion comprises at least about 90 mole percent chloride, the balance, if any, being bromide. Such preferred emulsions provide particularly good results in eliminating drag streaks and dot distortions. The silver halide emulsion can also contain a small amount of iodide, e.g., less than about 5 mole percent, if desired. Silver halide emulsions comprising 100 mole percent chloride have also been found to be quite useful.

The silver halide emulsion layer of the high-contrast photographic elements which can be processed according to the instant invention can contain any of hydrophilic water-permeable binding materials suitable for this purpose. Suitable materials include gelatin, colloidal albumin, polyvinyl compounds, cellulose derivatives, acrylamide polymers, etc. Mixtures of these binding agents can also be used. The binding agents for the emulsion layer of the high-contrast photographic element can also contain dispersed polymerized vinyl compounds. Such compounds are disclosed, for example, in U.S. Pats. Nos. 3,142,568 of Nottorf issued July 28, I964; 3,193,386 of White issued July 6, I965; 3,062,674 of Houck, Smith and Yudelson issued Nov. 6, I962; and 3,220,844 of Houck, Smith and Yudelson issued Nov. 30, I965; and include the water-insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates, interpolymers of alkyl acrylates with acrylic acids, acryloyloxy alkyl sulfonic acids, acetoacetoxy alkyl acrylates such as 2- acetoacetoxyethyl methacrylate and the like. These compounds can also be incorporated into a separate layer of the photographic element. The vinyl polymers are generally employed in concentrations in the range of about 20 to about 80 percent, most often concentrations at least about 50 percent, by weight, based on the weight of the binding agent. Silver halide emulsions wherein the binding agent contains a dispersed polymerized vinyl compound provide particularly good results in eliminating drag streaks and dot distortions.

As indicated above, the high-contrast photographic elements processed according to the instant invention contain at least about grams of a cadmium salt per mole of silver in the silver halide emulsion. While the cadmium salt is generally present in the silver halide emulsion, it can be incorporated into a contiguous layer if desired. Any cadmium salt can be used in the instant invention which is effective for the intended purpose. Generally, good results are achieved with water-soluble salts of cadmium such as cadmium chloride, cadmium acetate, cadmium nitrate, cadmium sulfate, etc. Especially good results are achieved with cadmium chloride. The concentration of the cadmium salt to be used depends, of course, upon the particular cadmium salt chosen as well as its location in the photographic element. Generally, at least about 10 grams of cadmium salt per mole of silver in the silver halide emulsion should be used. A useful concentration range for the cadmium salt is from about 10 to about 30, preferably about 13 to about 20, grams of cadmium salt per mole of silver in the silver halide emulsion.

The silver halide emulsion of the high-contrast photographic elements which can be processed according to the instant invention can be coated on a wide variety of supports. Hydrophilic colloid layers can be coated on one or both sides of the support, if desired. Typical supports are cellulose nitrate film, cellulose ester film, polyvinyl acetal film, polystyrene film, poly(ethylene terephthalate) film, and related films or resinous materials, as well as glass, paper, metal and the like. Supports such as paper, which are coated with aolefin polymers, particularly polymers of a-olefins containing two or more carbon atoms, as exemplified by polyethylene, polypropylene, ethylene-butene copolymers and the like can also be employed.

The silver halide emulsions of the high-contrast photographic elements which can be processed according to the instant invention can be sensitized using any of the well-known techniques in emulsion making, for example, by digesting with naturally active gelatin or various sulfur, selenium, tellurium compounds and/or gold compounds. The emulsions can be sensitized with salts of noble metals of Group VIII of the Periodic Table which have an atomic weight greater than 100. The emulsions can also contain addenda which increase speed and/or contrast such as quaternary ammonium salts, polyethylene glycols, thioether sensitizers or combinations thereof.

The silver halide emulsion of the high-contrast photographic elements which can be processed according to the instant invention can conveniently be orthosensitized or pansensitized with spectral-sensitizing dyes. For instance, these emulsions can be spectrally sensitized by treating with a solution of a sensitizing dye in an organic solvent. Sensitizing dyes useful in sensitizing such emulsions are described, for example, in US. Pats. Nos. 2,526,632 of Brooker and White issued Oct. 24, 1950, and 2,503,776 of Sprague issued Apr. 11, I950. Spectral sensitizers which can be used are the cyanines, merocyanines, complex (trinuclear) cyanines, complex (trinuclear) merocyanines, styryls, and hemicyanines.

The silver halide emulsion of the high-contrast photographic elements which can be processed according to the instant invention can also contain conventional addenda such as gelatin plasticizers, coating aids, antifoggants such as the azaindines and hardeners such as aldehyde hardeners, e.g., formaldehyde, mucochloric acid, glutaraldehyde bis(sodium bisulfite), maleic dialdehyde, aziridines, dioxane derivatives and oxypolysaccharides.

Other methods for reducing or eliminating drag streaks and dot distortions in continuous transport processing machines are found in application Ser. No. 661,532 of my coworker Masseth, filed concurrently herewith and entitled Photographic Developer Composition and Process of Using Same"; application, Ser. No. 661,530 of my coworker Salesin, filed concurrently herewith and entitled High-Contrast Photographic Elements and Method for Processing Same; and my application Ser. No. 66l ,53 l, filed concurrently herewith and entitled High-Contrast Photographic Elements and Method for Processing Same (Case A).

The following example will illustrate the invention but is not to be construed to limit it in any way.

EXAMPLE A fine-grain silver chlorobromide gelatin emulsion containing 90 mole percent chloride, 9 mole percent bromide and 1 mole percent iodide is chemically sensitized with sulfur and gold compounds. To various portions of the emulsion are added 6.5, 10 and 13 grams ofcadmium chloride per mole of silver. The emulsions are then coated on a polyethylene terephthalate support at a coverage of 470 milligrams of silver per square foot and 466 milligrams of gelatin per square foot. A normal gelatin overcoat of 82.5 milligrams of gelatin per square foot is coated over the emulsions.

The coated elements are then exposed, using tungsten illumination, to a step wedge through a magenta contact screen. The elements are then processed, using the development times listed below, in a Kodalith Roller Transport 324 Film Processor, of the type shown in US. Pat. No. 3,025,779 of Russell and Kunz issued Mar. 20, I962, employing the following developer which is disclosed and claimed in my coworker Masseths copending application, Ser. No. 661,532, filed concurrently herewith and entitled Photographic Developer Composition and Process of Using Same:

Sodium-bis-(Z-hydroxyethyll- Sodium formaldehyde hisulfite and 2,2

-lminodicthanol can be used to form this compound in situ.

The following results are obtained:

Slope of the straight line between two points which are 0.3 log E apart on the D vs. log E curve, where the lower point has a density of 0.1 above log.

The above results indicate that employing at least grams of a cadmium salt per mole of silver in the silver halide emulsion increases speed and effective contrast and considerably reduces drag lines for high-contrast elements processed in the above manner. The time-development H and D curves of the element containing at least 10 grams of cadmium salt per silver mole are also closer together, as evidenced by the relative speed change, thus providing a distinct advantage for machine processing which would be less sensitive to variations in processing time.

Although the invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, variations and modifications can be effected within the spirit and scope of the invention as described hereinbefore and as defined in the appended claims.

lclaim:

1. In a continuous process for processing an exposed, highcontrast, photographic element comprising a support coated with a silver halide emulsion layer, said halide comprising at least about 50 mole percent chloride, said element being processed in one continuous motion by transporting it into, through and out of at least one processing solution, the improvement comprising developing said element in a liquid developer composition comprising a developing agent and a carbonyl bisulfite-amine condensation product, said element containing in said silver halide emulsion at least about 10 grams of a cadmium salt per mole of silver.

2. The process of claim 1 wherein said developing agent is a dihydroxybenzene developing agent and said carbonyl bisulfite-amine condensation product is a formaldehyde bisulfite-amine condensation product.

3. The process of claim 2 wherein said dihydroxybenzene developing agent is present in a concentration of from about 0.05 to 0.50 mole per liter of developer composition and said formaldehyde bisulfite-amine condensation product is present in a concentration of from about 0.10 to about [.0 mole per liter of developer composition.

4. The process of claim 3 wherein said halide of said silver halide emulsion layer comprises at least about mole percent chloride.

5. The process of claim 4 wherein said cadmium salt is cadmium chloride.

6. The process of claim 4 wherein said dihydroxybenzene developing agent is hydroquinone.

7. The process of claim 6 wherein said cadmium salt is cadmium chloride.

8. The process of claim 6 wherein said formaldehyde bisulfite-amine condensation product is sodium bis(2-hydroxyethyl)aminomethane sulfonate.

9. The process of claim 8 wherein said cadmium salt is cadmium chloride.

10. The process of claim 4 wherein said photographic element is transported by rollers.

11. The process of claim 10 wherein said cadmium salt is cadmium chloride.

12. The process of claim 11 wherein said cadmium chloride is present in a concentration of from about 13 to about 20 grams r mole of silver insaid silver halideemulsion.

13. he process of claim 4 wherein said cadmium salt IS present in a concentration of from about 10 to about 30 grams per mole of silver in said silver halide emulsion.

14. The process of claim 13 wherein said cadmium salt is cadmium chloride. 

2. The process of claim 1 wherein said developing agent is a dihydroxybenzene developing agent and said carbonyl bisulfite-amine condensation product is a formaldehyde bisulfite-amine condensation product.
 3. The process of claim 2 wherein said dihydroxybenzene developing agent is present in a concentration of from about 0.05 to about 0.50 mole per liter of developer composition and said formaldehyde bisulfite-amine condensation product is present in a concentration of from about 0.10 to about 1.0 mole per liter of developer composition.
 4. The process of claim 3 wherein said halide of said silver halide emulsion layer compRises at least about 90 mole percent chloride.
 5. The process of claim 4 wherein said cadmium salt is cadmium chloride.
 6. The process of claim 4 wherein said dihydroxybenzene developing agent is hydroquinone.
 7. The process of claim 6 wherein said cadmium salt is cadmium chloride.
 8. The process of claim 6 wherein said formaldehyde bisulfite-amine condensation product is sodium bis(2-hydroxyethyl)aminomethane sulfonate.
 9. The process of claim 8 wherein said cadmium salt is cadmium chloride.
 10. The process of claim 4 wherein said photographic element is transported by rollers.
 11. The process of claim 10 wherein said cadmium salt is cadmium chloride.
 12. The process of claim 11 wherein said cadmium chloride is present in a concentration of from about 13 to about 20 grams per mole of silver in said silver halide emulsion.
 13. The process of claim 4 wherein said cadmium salt is present in a concentration of from about 10 to about 30 grams per mole of silver in said silver halide emulsion.
 14. The process of claim 13 wherein said cadmium salt is cadmium chloride. 